Chemistry

Chemistry

Problem

Combustion of methane proceeds according to CH4(g)+2 O2(g)⟶CO2(g)+2 H2O(l).\text{CH}_4(g)+2\,\text{O}_2(g)\longrightarrow \text{CO}_2(g)+2\,\text{H}_2\text{O}(l). The measured enthalpy change for one mole of CH4\text{CH}_4 combusted is  ⁣−890 kJ\!-890\,\text{kJ}. Given ΔHf∘[CO2(g)]=−393.5 kJ mol−1\Delta H_f^\circ[\text{CO}_2(g)]= -393.5\,\text{kJ}\,\text{mol}^{-1} and ΔHf∘[H2O(l)]=−285.8 kJ mol−1\Delta H_f^\circ[\text{H}_2\text{O}(l)]= -285.8\,\text{kJ}\,\text{mol}^{-1}, which value is closest to ΔHf∘[CH4(g)]\Delta H_f^\circ[\text{CH}_4(g)]? a) +1.85×102 kJ mol−1+1.85\times10^{2}\,\text{kJ}\,\text{mol}^{-1} b) −2.86×102 kJ mol−1-2.86\times10^{2}\,\text{kJ}\,\text{mol}^{-1} c) −7.5×101 kJ mol−1-7.5\times10^{1}\,\text{kJ}\,\text{mol}^{-1} d) +7.5×101 kJ mol−1+7.5\times10^{1}\,\text{kJ}\,\text{mol}^{-1}

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